Predict rolling-bearing fatigue life from load and speed — equivalent dynamic load, basic L10 in revolutions and hours, reliability-adjusted life, and a load–life curve that shows just how sharply life falls as load climbs.
Catalog value for the specific bearing number.
Used for the static safety check under peak load.
Tip: shaft load T₁+T₂ from a belt drive goes straight into Fr.
If Fa/Fr ≤ e, axial load is ignored and P = Fr. X, Y, e come from the bearing table.
Common: 20 000–40 000 h continuous, 8 000–12 000 h intermittent.
Life falls with the cube (ball) or 10/3 power (roller) of load — doubling the load cuts life ~8× or ~10×. Your operating point is marked; the dashed line is your target life.
Equivalent load. If Fa/Fr > e, P = X·Fr + Y·Fa; otherwise P = Fr. An application factor f_d multiplies P to account for shock beyond the steady load. X, Y and e are bearing-specific — read them from the manufacturer's table (defaults shown are typical single-row deep-groove ball values).
Basic life. L10 = (C/P)^p × 10⁶ revolutions, with p = 3 for ball and 10/3 for roller bearings. In hours: L10h = 10⁶ / (60·n) · (C/P)^p.
Adjusted life. Lna = a₁ · L10h, where a₁ sets the reliability (0.90→1.0, 0.95→0.62, 0.99→0.21). This tool applies the reliability factor only; the full ISO 281 a_ISO for lubrication and contamination is not modeled — real clean, well-lubricated bearings can exceed these numbers, dirty ones fall short.
Static check. Static safety S₀ = C₀ / P₀ guards against brinelling under peak/stationary load (here P₀ ≈ P). Rules of thumb: S₀ ≥ 1 for smooth, ≥ 1.5 for normal, ≥ 2–3 for shock duty.
Required rating. The C needed to hit your target life: C_req = P · (L10h_target · 60·n / 10⁶)^(1/p) — pick a bearing whose catalog C meets or beats it.